Pressure operated switch



Mm 22, 1938. H4 FROHMAN 2,111,969

PRESSURE OPERATED SWITCH Filed April 15, 1937 HARRY FROHMAN 3% AWENTOR such as set screws l2.

Patented Mar. 22, 1938 UNITED STATES PATENT OFFICE Brown Grease Gun N. 0., a corporation Corporation, Charlotte,

of North Carolina Application April 13, 1937, Serial No. 136,633

3 Claim.

This invention relates to a pressure operated switch which is adapted to be inserted in any fluid pressure line for automatically controlling a motor which in turn, creates a pressure. in the line. In fluid pressure lines it is very often desirable to maintain the pressure within predetermined limits. This is especially truein case of a grease dispensing apparatus where measured quantities of grease are delivered to a hearing such as a shackle in a motor vehicle and a high pressure is essential in order to efiect the delivery.

It is therefore, an object of this invention to provide a fluid pressure operated switch for controlling a motor circuit which in turn, drives'a pump for maintaining a pressure in a line.

It is a further object of this invention to provide a switch of the class described with means for varying the point at which said switch will make or break contact. By providing this adjusting means, it is possible to select a range of pressures within which the switch is adapted to operate thereby making the switch capable of being used under varied conditions.

Some of the objects of the invention having been stated, other objects will appear when taken in connection with the accompanying drawing, in which:

Figure 1 is a perspective view showing one side of the invention;

Figure 2 is a perspective view of the invention looking at a different angle from that in Figure l;

Figure.3 is an isometric view with portions thereof broken away showing the structure enclosed in the housing; t

Figure 4 is an elevation of the invention showing the switch operating mechanism disposed therein in section;

Figure 5 is a sectional detail view of the contact washer on insulation rod.

Referring more specifically to the drawing, the numeral I0 indicates a suitable housing in which a fluid pressure operated switch is adapted to be mounted. This housing has a cover plate ll removably secured thereon by any suitable means Suitable holes are provided in upwardly projecting lugs Illa which are integral with the housing III to provide means for securing the housing to some object.

A pair of wires l3 and I4 lead into the housing l0 and are connected to terminals l5 and I 6 respectively, said terminals being threadably secured in insulation cylinder block IT. This block I I has one end thereof secured in T-shaped memberv I8, which member is threadably secured around the intermediate portion of longitudinally disposed rod l9. This rod has its ends rotatably mounted in the housing I0. In order to provide means for moving the T-shaped member 18 and its associated cylinder l'l longitudinally of the housing ID a knurled knob 20 is disposed on one 5 end of the rod and on the exterior of the housing. This knob may be turned in the desired direction to cause the members l1 and Hi to move back and forth within the housing I0, thereby determining the point at which the circuit will be made or broken. A conductive washer 25 is loosely secured on one end of insulation rod 26, both the rod and the bar 25 being slidably mounted in bore Ila within cylinder IT. The washer 25 is held on rod 26 by screw 25a as shown in Fig- 15 ure 5, thus allowing contact with both contacts I5 and I6, even though they may be of different lengths. The rod 26 is also supported by a plug 21 which is secured in the end of cylinder ll by means such as set screw 28. In the present position of bar 25, no contact is being made between terminals I5 and I6 since a sufficient pressure has been generated to cause the bar to be removed to the left and away from these terminals,

The mechanism for actuating the rod 26 and bar 25 comprises a forked bar 30 which has its upper end resting astride the end of rod 26 and has its lower end secured around pressure rod 3| between collars 32 and 33. In order to hold the upper forked end of bar 36 intact with the rod 26 as rod 3| moves to the left a suitable washer 34 and a cotter pin 35 has been provided on the end of rod 26. The switch bar 25 and rod 26 are held in cont-act with the terminals l5 and i6 by means of a compression spring 36 which is 35 disposed around rod 26 and has one end thereof engaging the bar 25 and its other end engaging the plug 21. In other words, this spring acts against the pressure and when the circuit is broken between the terminals l5 and 16.

The rod 3| has the left-hand end thereof slidably mounted in the end of casing It. A second compression spring 31 is mounted around rod 31 between the casing in and the collar 32, which spring normally tends to force the rod 3| to the right in Figure 4. The right-hand end of the rod Si is slidably mounted in cylinder 38 which cylinder has a bore 39 therein. The bore 39 has; communicating therewith a restricted bore in which is slidably mounted pin 46 which pin is integral with the right-hand end of rod 3|. The restricted bore in which the pin 46 is mounted has a second bore communicating therewith in which a packing gland M is mounted. This gland has adjacent its right-hand end a slidably mounted sleeve 42 which houses the extreme right-hand portion of pin 40. 'Ihe cylinder 88 is threadably secured in the end of housing I and has secured in the end thereof a pipe fitting 43 to which a pressure line is secured. when the pressure is applied to this line, the pin 4. and its associated piston rod 3! is moved to the left in Figure 4. thereby causing the member 80 to move the rod ll and the contact bar 2! to the left and break the circuit which will, in turn, stop the motor.

when the pressure has been relieved the rod ii and its associated parts will move back to the right which will allow the spring in cylinder 36 to move the contact bar 25 into contact with terminals I and it to start the motor again.

It is seen that the right-hand end of pin 40 (Fig. 4) is the only area upon which the pressure is applied; consequently, the spring 31 will not have to be of very great strength since the area upon which the pressure acts is very small. Furthermore, since the sleeve 42 is slidably mounted in the right-hand end of the member II and contacts the packing gland Ii, this gland will naturally be compressed around the pin ill to prevent any leakage of the pressure.

The T-shaped member II has secured thereto an L-shaped indicator 5 which penetrates a slot 48 in the housing Iii. The upper end of the indicator is pointed and disposed over a scale 41 on plate 48. By turning the nut and its associated parts, this indicator will be moved back and forth over the scale 41 to indicate the point at which the switch will be disconnected.

It is evident that the location of the cylinder i9 relative to pressure cylinder ll determines the amount of pressure necessary to be set up within the cylinder 38 to cause the contact to be broken. In other words, the nearer the cylinder i1 is disposed to the left-hand end of housing II, the more will be the pressure necessary to compress spring 31 so that the contact 35 will be moved away from terminals l5 and I. In order to limit the amount that the cylinder I! may be moved to the right in the housing Ill, a suitable set screw 49 is provided which acts as an adjustable stop for contacting the end of the cylinder.

It is therefore seen that I have provided a fluid pressure operated switch for controlling the pressure between predetermined limits in a pressure line with means for varying the point at which the switch will be operated. In this case the limits between which the built up pressure can be relieved from the pressure line without again making contact and starting the motor is necessarily small, but there is a short pressure range after the switch has been disconnected in which pressure may be used without allowing the switch to move back again to the connected position. This pressure range is produced by the momentum of the motor which creates a pressure within the pressure lines. At the time of the disconnecting of the bar 25 from the contacts l5 and IS the contact bar is moved an appreciable distance away from the terminals which distance is again traversed by the bar 25 as the pressure is relieved before contact is made. This short distance, while only a matter of a fraction of an inch in a switch used in'an ordinary grease dispensing apparatus, represents the range of pressure which may be utilized without again starting the motor. It is very undesirable to have a wide pressure range, especially where a maximum pressure is desired to be available at all times. a

It is evident that after pressure has been built up to open the switch that the pressure generated by the motor has not all reached the piston 40 and thus after the circuit is broken this belated pressure will open the switch to a greater degree and thus provide a working range.

In the drawing and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only, and not for purposes of limitation, the scope of the invention being set forth in the appended claims.

I claim:

I. A pressure operated electrical switch comprising a casing, a cylinder of insulating material disposed in said casing, a pair of contacts in the base of said cylinder, a rod of insulating material disposed in said cylinder and having a metallic disk on one end thereof adapted to contact said pair of contacts, a threaded rod disposed in said casing. a support for the cylinder threadedly mounted on said threaded rod, a pressure line leading into said casing, a piston disposed in said pressure line, a compression spring normally forcing said piston against the pressure in said pressure line, a projection carried by said piston having a forked end disposed around said insulating rod, means on the insulating rod adapted to be engaged by said projection to move the disk on the rod out of contact with said pair of contacts when a predetermined pressure has been created in the pressure line.

2. A pressure operated switch comprising a casing, a threaded rod disposed in said casing. a switch threadahly mounted on said threaded rod. a pressure line leading to said casing, a piston in said pressure line and extending into said casing. means on the piston for engaging said switch and opening the same upon a predetermined high pressure being present in the pressure line, compression means tending to normally close said switch, and spring means for moving the piston to allow the compression means to close said switch upon a predetermined low pressure being reached in the pressure line.

'3. A pressure operated switch comprising a casing, a rod disposed in said casing, a switch adjustably mounted on said rod, a pressure line leading to said casing, a piston in said pressure line and extending into said casing, means on the piston for engaging said switch and opening the same upon a predetermined high pressure being present in the pressure line, compression means tending normally to close said switch. and spring means for moving the piston to allow the compression means to close said switch upon a predetermined low pressure being reached in the pressure line.

HARRY FROHMAN. 

